Abstract:
An integrative taxonomic study was conducted on two ciliate species belonging to the order Kentrurostylida Paiva, 2020 (subclass Hypotrichia Stein, 1859),
Pseudourostyla cristata (Jerka-Dziadosz, 1964) Borror, 1972 and
Anteholosticha adami (Foissner, 1982) Berger, 2003, collected from East Lake, Wuhan, Hubei Province, China, based on morphological and molecular phylogenetic evidences. The morphological characteristics of the East Lake population of
P.
cristata agree well with those of previously reported populations. The present study further clarified the morphogenetic processes and developmental origins of the oral apparatus, frontoventral-transverse cirri, marginal cirri, and dorsal kineties. Phylogenetic analysis based on the SSU rRNA gene sequences placed
P.
cristata within the order Kentrurostylida. The East Asian populations showed low genetic divergence, with sequence similarities of 99.8%—100%. Although the Korean population (GU942569) contained a continuous deletion of more than 100 bases, only two nucleotide differences were detected outside the deleted region. The Indian population exhibited greater sequence divergence from the East Asian populations, with similarities of only 98.1%—99.4%, suggesting that their taxonomic status requires further investigation. The East Lake population of
A.
adami represents the first record of this species from a freshwater habitat. Morphological comparison showed that this population is highly consistent with the Austrian type population and other well-described populations, differing only slightly in several meristic characters. The phylogenetic tree also placed
A.
adami within Kentrurostylida, while species assigned to
Anteholosticha were scattered across different clades, further supporting non-monophyletic of the genus. This study supplements the morphogenetic data of
P.
cristata, reports the first SSU rRNA gene sequence of
A.
adami, and expands the ranges of morphological variation, geographic distributions, and habitat information of the two kentrurostylid ciliates, providing new evidence for the taxonomic delimitation and phylogenetic relationships of this group of ciliates.